Thursday, March 29, 2012

The Storm Prediction Center has outlined a risk of severe weather for 4 days out in the Southern Plains. I say 4 days out, because 'Day 1' is today, 'Day 2' is tomorrow, etc.

The perpetrator for this severe weather will involve a dry line. This dry line will be stationed in central Texas. As the warm air is drawn north by the storm system located in Wisconsin, the dry line will quickly accumulate a dew point gradient. When the cold front out to the west intercepts this gradient, showers and thunderstorms should be quick to form in Arkansas, Louisiana, and probably some more discrete, severe storm cells out ahead of the system.
As the storm system moves east, wind shearing will increase to a good 60 knots, easily sustainable for tornadoes. This shearing will be accompanied by at least 1000 j/kg of instability. The combination will probably make for some discrete super cells in due time.
There does look to be a fairly weak cap over the area, about 100 -j/kg. This should be easily broken by the storm system.
As the system makes its way eastward, it will try to attain a negative tilt. However, based on the latest GFS, that is possible, not confident. The GFS has the storm take on a neutral/slight negative tilt when it is in the area being monitored for severe weather.

Hello everyone, I'm here to present to you the 2012 Atlantic Hurricane Forecast.

Let's get right to it and look at something called the TNA. The Tropical North Atlantic index, or TNA, is based on looking at sea surface temperatures (SST). In areas of above normal SST's, the TNA will be positive. In areas of below normal SST's, the TNA will correspond negatively.

Past TNA

Here's the total past TNA recorded values. As you can see, the majority of 1981-1997 was in a general cooler phase, while 1998-current has been a mainly warmer phase. This does raise questions on if global warming has played a role in this, but that is not nearly what this forecast is on.
Notice how strongly positive the TNA was from 2009 to about 2011. Here's a brief analysis concerning those hurricane seasons.

The reason this is significant is because El Ninos tend to reduce hurricane activity in the region, while La Ninas can strengthen Atlantic tropical activity. The TNA and La Nina combined in 2010 to produce the 3rd most active hurricane season on record.

This attention to the ENSO (La Nina/El Nino) conditions brings us to the question of which condition will we have this hurricane season.
At the moment, we are in a neutral ENSO state, pretty much meaning the 'silver lining' between an El Nino or La Nina. This, to me, means that the effects of the ENSO will not be a real factor, because another way neutral ENSO can be interpreted as is a very weak La Nina/El Nino, although this view point can lead to more issues than solutions with understanding.

Here's the latest SST anomalies for the Caribbean and Gulf of Mexico. While the Caribbean is not too impressive, check out how warm the Gulf of Mexico is! Many areas are over 2 degrees above normal. While that may not seem like a lot, it may have some potentially catastrophic effects on any tropical activity that forms in the Gulf. If a cyclone does form, it will have all of that warm water to use to strengthen.

All of that said, here's my forecast.

I am expecting an above normal hurricane season with a strong positive TNA combined with very weak, if nonexistent ENSO effects. A very warm Gulf also adds to the forecast. I put the chance for a landfalling US hurricane at 65%, because we are overdue (which honestly adds nothing to where hurricanes go), but mainly due to the very warm Gulf of Mexico.

Winter's potentially final snowfall will fall in the Northeast tomorrow, with a general 1-4 inches of snow expected across the region.
This snow will fall as a storm system makes its way eastward across the US and manages to pass across some moisture that meets up with some cold air to make snowfall for the Northeast. Again, nothing major, just a few inches to satisfy those in the Northeast that got very little snow over the course of this past 'winter'.

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